I know most people have inboards here but was hoping someone could help me out.

I have a '99 Sea Ray 210 BR with a 5.0L MPI Mercruiser and a Bravo 3 lower unit.

The other day the drive unit started to creep down very slowly. It doesn't stay raised and will settle down to the ground in just a few hours while parked.

It was working fine before this started and still works fine. It can hold itself up while we boat (if it goes down it is very slow). I use the trim a lot to help adjust the wake while the kids wake board.

I checked for leaks, both inside and outside the boat. If there are any leaks it is way under or behind the engine were I can't see it.

The trim fluid was right at the minimum level and I topped it off then ran the drive up and down a few times. I thought there might have been some air in there but that didn't help.

I called some dealers and was told the pump has check valves and they are know to cause problems. I was also told the cylinders can be leaking internally.

And, finally I was told that the cylinders have trim guides that deteriorate and put contaminants in the oil. And this is what gets stuck in the check valves. So I really need to replace (or rebuild) the pump as well as the cylinders.

Does anyone have any past experience with this issue? Any troubleshooting suggestions?